I. Technical Field
The present invention relates to a flexible semiconductor device and a method for producing the same.
II. Description of the Related Art
There is a growing need for a flat panel display as a display for the use of a computer with the spread of information terminals. With the further progress of informatization, opportunities of computerization of information increases with respect to information conventionally provided through paper medium. Accordingly, a need for electronic paper or digital paper is growing as a thin, light, handy mobile display medium (for example, JP-A-2007-67263).
In a typical flat panel display, a presentation medium is formed by using an element utilizing liquid crystal, an organic EL (organic electroluminescence), an electrophoresis, and the like. In the above presentation medium, in order to secure uniformity of a brightness of a screen, an image rewrite rate, and the like, a technique in which active drive element (for example, TFT element) is used as an image drive element comes into mainstream. For example, a conventional computer display includes the TFT element formed on a substrate so as to include a liquid crystal, an organic EL device, and the like sealed therein. Herein, a semiconductor made of a-Si (amorphous silicon), p-Si (polysilicon), and the like can be mainly used as the TFT element. The TFT element is produced such that the Si semiconductors (as well as a metal film, as required) are multilayered and a source electrode, a drain electrode, and a gate electrode are sequentially formed on a substrate.
Since the formation of the TFT element by using the above-mentioned Si materials includes a high-temperature process, a substrate material for such TFT element is limited to a material that can withstand the process temperature. Therefore, a material having an excellent heat resistance property, i.e., a glass substrate, is actually required in forming the substrate. A quartz substrate can also be employable here, but is expensive and thus has an economic concern in an increased size of the display. In view of the above, the glass substrate is generally used as the substrate of the TFT element.
However, when the above-mentioned thin display is made of the conventional glass substrate, the display becomes heavy and lacks flexibility, resulting in leaving the possible disadvantage that the glass substrate may be broken due to a drop impact. The above-mentioned characteristics resulting from the formation of the TFT element on the glass substrate are not desirable very much in satisfying the needs for a convenient handy thin display in the developing process for informatization.
To meet the need for a light thin display, a semiconductor device (i.e., flexible semiconductor device) in which the TFT element is formed on a resin substrate (i.e., plastic substrate) is developed in view of the flexibility and light weight of the substrate. For example, JP-A-2005-294300 discloses a technique in which the TFT element is formed on a support (for example, glass substrate) by the process substantially identical to the conventional process and is thereafter separated from the glass substrate to be transferred to the resin substrate. A formation of the TFT element without using the glass substrate as the resulting composition member is developed in a manner as described below. Namely, in the formation, the TFT element is initially formed on the glass substrate and the glass substrate mounted with the TFT element is bonded on a resin substrate through a sealing layer made of, for example, an acrylic resin. Subsequently, the glass substrate is separated therefrom to transfer the TFT element onto the resin substrate.